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This is about the simplest possible wiring plan if I wanted to replace the Klima with dumb relays and not screw something else up. Explanation:
- Pins 4 and 12 are the full throttle and high temp cutout signals. They present ground when either condition is satisfied. These pins get wired to a standard DIN relay, which is set up as NC. Pin 5 on the Klima is the power source for the whole system. Unless a problem is signaled, this relay will present 12v+ on 87a. This will be used to power the coil of the other relay.
- The diode is required to prevent the fan from coming on high speed when the throttle is floored.
- Pins 5&6 are kickdown control, they are simply bridged.
- Pin 10 presents ground when the CC head unit wants the compressor on. This controls the coil on the compressor relay.
- Pin 7 is the compressor clutch.
To sum up: the cutout relay will shut down the compressor relay if the accelerator is floored or if the high temp switch closes. Otherwise, the compressor relay is controlled by the pressure switch and the CC head unit.
Disadvantages:
- not sure if there are situations where the Klima shuts off the kickdown solenoid. The jumper bypasses control entirely.
- No 'belt protection' from the compressor sensor, but that was the goal so it's good/bad.
- Looking at it, I'm pretty bummed by how non-obvious it is. Anyone stumbling into it would really have a head scratcher. It took me a while to put it together, and it would take longer for someone reverse engineer. But I must admit, having spent twenty or thirty years reverse engineering Bosch cr_p, it's almost sweet revenge.
Just for the permanent record, the pinouts on the Klima are as follows:
1 Ground
2 Engine RPM
3 Not used
4 Accelerator microswitch (normally open/grounds at full throttle)
5 12V+ from fuse box, hot in run
6 Kickdown switch/solenoid
7 AC compressor
8 Not used
9 AC RPM Sensor (red)
10 Pressure switch (normally grounded)
11 AC RPM Sensor (white)
12 High temperature switch (normally open/grounded when too hot)
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